This invention relates to a process of preparing 2-trifluoromethylpropanol by vapor phase catalytic hydrogenation of the trimer of 2-trifluoromethylpropanal.
Wide uses have been found for 2-trifluoromethylpropanol as industrial material. For example, this compound is useful for esterification of various compounds. Furthermore, by using 2-trifluoromethylpropyl halides it is easy to prepare 2-trifluoromethyl derivatives of various compounds for the purpose of using the derivatives as important raw materials or precursors of some medicines, agricultural chemicals and fluorine-containing polymers.
It was once proposed to prepare 2-trifluoromethylpropanol by liquid phase reduction of methyl 2-trifluoromethylpropionate using lithium aluminum hydride as reducing agent. However, this method has not been put into industrial practice because it is necessary to use the reducing agent in an equimolar proportion to the starting material and, consequently, long and troublesome procedures are needed for isolation of the reaction product.
In general it is known that an aliphatic alcohol can be obtained by liquid phase reduction of a corresponding aliphatic aldehyde or ketone using a metal hydride as reducing agent, but industrially this knowledge has not been utilized either because of the need of using the metal hydride in an equimolar proportion to the starting material. It is also possible to obtain an aliphatic alcohol by hydrogenation of an aliphatic aldehyde or ketone using a metal catalytic such as platinum or palladium. However, it is difficult to apply this method to fluorinated aldehydes or ketones to obtain fluorinated alcohols, and in the cases of industrially favorable vapor phase catalytic hydrogenation very often it is utterly impossible to obtain the intended fluorinated alcohols by reason of significant side reactions and/or decomposition of once formed fluorinated alcohols. For example, U.S. Pat. No. 3,468,964 contains a description that neither 1,1,1,3,3,3-hexafluoropropane-2-ol nor 2,2,2-trifluoroethanol can be obtained by vapor phase contact reaction of hexafluoroacetone or trifluoroacetoaldehyde with hydrogen in the presence of platinum catalyst.
When it is intended to prepare 2-trifluoromethylpropanol by hydrogenation of 2-trifluoromethylpropanal, particularly great difficulties are present because the latter compound is quite liable to undergo association so that not only the monomer having the aldehyde structure of Formula (I) but also an associated polymer, which is usually a trimer having the cyclic ether structure of Formula (II), must be converted to 2-trifluoromethylpropanol. ##STR1##